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The number of deaths linked to cantaloupes contaminated with the Listeria monocytogenes bacteria has risen to 21, the Centers for Disease Control and Prevention said Friday.

At least 109 cases of listeria have been reported in 24 states, the agency said. That's nine more cases and four more states than it reported Tuesday. The number of deaths has risen by three.

Health officials have said the number of cases could continue to grow, citing reporting lags and the fact the disease can develop slowly in some people, taking up to two months.

The listeria outbreak is the deadliest food-borne illness outbreak in the United States since 1998.

Five people each have died in New Mexico and Colorado from consuming the tainted fruit, along with two people each in Kansas and Texas and one in Indiana, Maryland, Missouri, Nebraska, New York, Oklahoma and Wyoming, the CDC said. In addition, one woman who was pregnant at the time of the illness had a miscarriage.

Cases have also been reported in Alabama, Arkansas, California, Idaho, Illinois, Montana, North Dakota, Oregon, South Dakota, Texas, Virginia, West Virginia and Wisconsin.

Groups at high risk for listeria include older adults, people with weakened immune systems and pregnant women, officials have said.

The grower, Jensen Farms of Granada, Colorado, issued a voluntary recall of its Rocky Ford brand cantaloupes on September 14. The tainted cantaloupes should be off store shelves, the CDC said.

Cantaloupes from Jensen Farms should be disposed of immediately, even if some of them have been eaten, the CDC said. If consumers are uncertain about the source of a cantaloupe, they are urged to ask their supermarket. If the source remains unknown, the fruit should be thrown out, officials have said.

Refrigerating a cantaloupe will not kill the bacteria, which can grow at low temperatures, authorities have said, and consumers should not try to wash off the bacteria.